A crawlspace is a low or narrow space, such as one beneath the upper or lower story of a building that gives workers access to items such as plumbing or wiring equipment. In residential structures, typically, this space is defined by the structures foundation walls so that the crawlspace is enclosed under the lowest floor of the structure. Foundation walls are generally composed of concrete blocks or poured concrete walls. The bottom of the crawlspace is generally ground, which in most cases is simply dirt or sand. In other cases, the ground floor may be poured concrete. The floor above the crawlspace is generally made of wood. Additionally, the crawlspace dirt floor is generally lower then the soil surrounding the structure. Further, the crawlspace is generally not well insulated, and due to leaks, cracks and vents, is generally exposed to the outside environment.
Due to limited air flow in a crawlspace, moisture that seeps out of the ground and into the crawlspace causes the crawlspace to become damp and may stay damp for extended periods of time. This moisture can be very damaging to the structure's foundation walls, floor joists, and other structural components, often leading to premature deterioration of the structure and costly repairs. Additionally, mold, mildew, insects and other undesirable conditions can develop in the crawlspace which can affect the foundation walls and produce an unhealthy environment for inhabitants within the living spaces of the structure above. Additionally, the non-insulated crawlspace allows for the temperature differential between the living space of a home and the crawlspace to approach or be equal to the temperature differential between the living space and the outdoors.
Due to the enclosed nature of the crawlspace, volatile materials, such as construction grade adhesives, that create a hazardous environment, whether through flammable vapors or toxic fumes, is highly undesirable for poorly ventilated spaces. For example, adhesives that produce toxic fumes or flammable vapors are not desirable to use on foundation walls as they can accumulate in the crawlspace, creating a fire hazard due to low ventilation.
Further, such undesirable contaminants in the crawlspace can flow into the air of the structure itself. The natural air flow in a structure is from bottom to top. Based on the principal that warm air rises, as the air in the structure heats up, it moves up through the structure. Once this warm air makes it way up to the attic and roof levels, it will normally be vented out though the soffits or a ridge vent. Much of the air that flows in a structure comes from the crawlspace. In older, more “leaky structures”, the air exchange rate can be as high as two air changes per hour. It has been estimated that up to half of the air you breathe on the first floor of a structure is air that came from the crawlspace. If there is high humidity in the crawlspace, there will be higher humidity in the living space. If there is mold and mildew in the crawlspace, there could be mold and mildew in the structure.
Additionally, when air leaks through the foundation walls into the crawlspace and flows into the living space, the temperature differential can undesirably heat or cool the living space therefore requiring more energy to maintain the temperature in the living space. Historically, the design of the crawlspace requires that the crawlspace be open with vents so that air flow can occur in the crawlspace. These vents are an attempt to reduce moisture in the crawlspace. However, these vents allow ambient air to enter the crawlspace.
By providing a vapor barrier to the foundation wall, much of the moisture that enters a crawlspace can be eliminated. A problem arises in that typical construction adhesives capable of securing a plastic liner to a concrete foundation wall have high VOC levels and emit dangerous amounts of toxic and flammable vapor, which is a fire hazard for an enclosed area such as a crawlspace. To avoid the use of such dangerous adhesives, mechanical fasteners have been required to secure the vapor barrier to the foundation wall. This typically involves drilling into the foundation walls to properly secure the vapor barrier to the foundation walls. Installation of such systems has thus largely been limited to professional installers with the tools and abilities to accomplish such a task.
Further, it is desirable for the barrier to contain an antimicrobial property to provide additional protection against undesirable items such as mold and bacteria. With the proper barrier, moisture levels and air infiltration can be better controlled resulting in less of a chance for mold and mildew growth, wood rot, and insects and animals entering the crawlspace.
While there have been several efforts to provide proper barriers for crawlspaces, the installation of these barriers has proven challenging. One principal factor contributing to the difficulty is that the environment of the crawlspace makes adhering the barrier to the foundation walls challenging.
One method for securing the barrier to the foundation walls is disclosed in U.S. Pat. No. 6,575,666. This patent discloses a crawlspace encapsulation system the uses nylon fasteners to secure and support the liner vertically on the foundation walls. The patent states that adhesive tape or a suitable adhesive caulk composition is used to seal the end of the vapor barrier against the top side of the foundation walls, but not to mount or support the liner on the walls. This is because low VOC adhesives suitable for holding to the foundation walls are not suitable for adhering to plastic liners of the type used in crawlspaces. For example, a concrete adhesive, while working well for concrete, does not adhere well to plastic film, particularly the type used for vapor barriers. This difficultly with adhesion is compounded when the plastic film is treated with an antimicrobial substance. Therefore, there is a need for a system for securing a vapor barrier to a foundation wall that does not require mechanical fasteners or high VOC adhesives. Thus, it would be advantageous to have adhesive and other materials for enclosing a crawlspace having desirable fire retardants and low volatile organic compound (VOC) levels.
Accordingly, it is an object of the present invention to provide a system for permanently securing a vapor barrier to a foundation wall using a low VOC adhesive.
It is a further object of the present invention to provide a vapor barrier having fire retardant and antimicrobial properties.